780 



THE DUCKWEED FAMILY. 



II. ACORUS. ACORUS. 



A single species, distinguished as a genus by the leaf-like spatha 

 not enclosing the spike, and by the numerous hermaphrodite flowers 

 consisting of a perianth of 6 short scales, 6 stamens, and a 2- or 3-celled 

 ovary, all closely packed in a dense, cylindrical spike. 



1. Sweet Acorus. Acorus calamus, Linn. (Fig. 937.) 



(Eng. Bot. t. 356. Sweet Flag. Siveet Sedge.) 



A highly aromatic, reed-like plant, 

 with a thick, shortly creeping rootstock. 

 Leaves linear and erect, 2 or 3 feet long, 

 about half an inch broad. Flowering- 

 stem simple and erect, the long, linear, 

 leaf-like spatha forming a flattened con- 

 tinuation, with the spike sessile at its 

 base so as to appear lateral ; it is cy- 

 lindrical, very dense, 2 to 3 inches long, 

 of a yellowish-green colour. 



On the edges of lakes and streams, all 

 over Europe, except the extreme north ; 

 rare in the most western States, but ex- 

 tends all across Russian and central Asia 

 into North America. In Britain, be- 

 lieved to be indigenous only in some of 

 the eastern counties of England, but has 

 been introduced into many parts of Eng- 

 Fig. 937. land and southern Scotland. Fl. sum- 



LXXVI. THE DUCKWEED FAMILY. LEMNACE.E. 



A single genus, united by some with the Arum family, but 

 anomalous in its mode of vegetation and very reduced flowers. 



I. DUCKWEED. LEMNA. 



Floating plants, without distinct stems or real leaves, but consisting 

 of small, leaf-like fronds, either separate or cohering two or three to- 

 gether by their edges, emitting one or more fibres from their under 



